Chart Update and ResetZoom

[Nico-DF]

Hi,

As I continue to work around with chartjs and the zoom plugin, I encoutered an issue with the latest version of zoom plugin.

Description

According to https://www.chartjs.org/docs/latest/developers/updates.html, One can use the update() method after updating either/both data and options to redraw the graph.

But now, probably due to a bug introduced by latest versions of ChartZoom plugin, if you update the data/scale and then perform a reset zoom, the scale would be reseted to the 1st options while options are still correctly pointing to latest data

Reproduction

A sample is available here:
https://codepen.io/Nico-DF/pen/poeKrRV

Do the following:

• Click on Update Data, it will update the data part and option containing scale and then use the update() function provided by Chartjs
• The new scale is now 10-12 (previously 0-2)
• Click on reset zoom
• The scale will be reseted to 0-2.

Trivia

I could trace it back to some code called by the resetZoom() function, it will use:

const originalScaleLimits = storeOriginalScaleLimits(chart);

Which in turn, calls:

const {originalScaleLimits} = getState(chart);

The getState is a shorthand to take back data from some WeakMap

function getState(chart) {
  let state = chartStates.get(chart);
  if (!state) {
    state = {
      originalScaleLimits: {},
      handlers: {},
      panDelta: {}
    };
    chartStates.set(chart, state);
  }
  return state;
}

It turns out that the chartStates map in the originalScaleLimits still contains the data of the chart used by the constructor.

I still have not tested it yet, but I guess that doing a .destroy() and recreate the whole graph would work but it would defeat the purpose of the update method.
Moreover, I think that the behavior was correct a few version ago (not tested to roll back yet; and if the behavior that I have described is indeed a buggy one)

[Nico-DF]

I checked as far as zoom v1.0.0-beta1 and chart 3.0.0 and the resetZoom behavior is the same, so it doesn't seem to be a regression